Bacteria is a group of microscopic, unicellular organisms that lack a distinct nucleus and reproduce by cell division. Bacteria typically range from 1 to 10 micrometers and vary in the ways they obtain energy and nourishment. About 200 species of bacteria are pathogenic, pathogenicity varies among the species and is dependent on both the virulence of the species and the condition of the host organism. The E. coli 0157:H7 and salmonella microorganisms are just two of the most well known pathogenic bacteria which may cause death in humans.
It is well known that bacteria is involved in the spoilage of food and in particular meat, wine, vegetables, milk and other dairy products. Bacteria may actually render such foods unpalatable by changing their composition. Bacteria growth can also lead to food poisoning such as that caused by clostridium botulinum or staphylococcus aureus. Certain types of bacteria are found in nearly all food products.
Bacteria can be aerobes or anaerobes and are capable of attaching to any surface. Under certain conditions, especially in food processing, bacteria can quickly form a microorganism which seeks a solid surface having nutrients for growth. As the microorganisms grow and multiply, the newly formed cells attach to each other as well as to the surface forming a confluent colony. When the colony becomes sufficiently large, it entraps debris, nutrients, and other microorganisms, wherein a microbial biofilm is established. A biofilm coating enhances the ability of bacteria to resist removal and inactivation. If a biofilm conceals a pathogenic bacteria, the result can lead to illness and death if the bacteria is later introduced to a human.
Common knowledge states that an emphasis must be placed on proper cleaning and sanitizing procedures, especially as those relate to food processing systems. Bacteria that enters a food processing system has an enhanced chance of being consumed by the public. Bacteria are controllable in food processing systems if an effective sanitization program is implemented. For this reason, a myriad of processes are known in the industry all with various levels of effectiveness.
Ozonation, being an allotropic form of oxygen, is used in purifying water, sterilizing air, and treating of foods and the creation of ice. Ozonated ice is commonly used for the storage of fish and chicken carcasses in an attempt to control such bacteria as Listeria monocytogenes. However, ozonated ice is only partially effective because of the naturally occurring biofilm that prevents the physical contact of released oxidants with the carcasses during storage. In addition, ozone can create a corrosive environment making it difficult to control.
Irradiation is another known process employed in many parts of the world with limited levels of acceptance and effectiveness. Questions currently remain as to the residual effects of products treated with irradiation and the consuming public. The process is also expensive making it impractical for many applications and limited for use on certain materials. In Europe special labeling requirements are imposed on those foods treated by irradiation with similar measures being considered in the United States.
Various types of acids are used in controlling bacteria, all having various levels of effectiveness. Acids are corrosive, dangerous to handle, and contact with a surface may alter the characteristic of the surface. Acids have limited effectiveness and are not considered effective prior to evisceration because of the nearly impermeable biofilms on the surface of carcasses. In addition, some acids cause taste and color degradation and are not environmentally friendly making disposal of the waste a major consideration. It should be noted that not all acids cause such reactions and those that do not, to any measurable degree, are often referred to as soft acids. However, soft acids are known to be most effective in post evisceration. Lactic acid is currently used in decontamination situations but teachings of the product are limited to destruction of bacteria before a biofilm develops. Once the biofilm develops, the acid is of limited use in spraying or dipping.
Physical removal also remains an option for bacteria control. However, the physical removal of visual contamination by trimming of effected areas, such as on carcasses, creates the risk of spreading the contaminants.
According to industry publications presented by Characklis and Cooksel in 1983 further supplemented by Characklis in 1984, set forth in Food Technology, Article of July 1994, Volume 48, No. 7, the biofilm is considered a five stage process which results from the physical, chemical and biological phenomenon and is identified as follows: transport of nutrients, inorganic, and organic matter to the solid surface; absorption of a conditioning film containing inorganic or organic nutrients; attachment of microbial cells to the wetted surface in initiation of growth; Bacterial metabolism within the biofilm; and cell disruption and detachment from the biofilm.
For these reasons, efforts are constantly under way to discover an economical and safe method for the destruction of bacteria. The problem is that the protective coating made by the biofilm requires treatment strong enough to break through the biofilm, destroy the underlying bacteria, yet not harm or alter the treated product.
What is lacking in the art is a process that is environmentally safe and specifically directed to the removal of the biofilm allowing for subsequent treatment of the underlying bacteria.